Conventionally, a vehicle, such as a hybrid vehicle and an electric vehicle, includes an electric power source that supplies power to a motor as a driving source. Because the aforementioned electric power source is configured to be insulated from a vehicle body, the vehicle is equipped with a monitoring device mounted thereon, which monitors an insulation state of the electric power source, in other words, which detects the deterioration of insulation resistance of the electric power source.
As such a monitoring device, there is known a monitoring device that employs a pulse application system that determines a deteriorated part of the insulation resistance by using application of a pulse. Specifically, when the ignition of a vehicle is turned off, the monitoring device generates a pulse by using a microcomputer and the like, and applies the pulse to a negative electrode (total minus) of a battery. When the pulse is applied in this manner, an electric current flows through an insulation resistance and a GrouND (GND) of the vehicle body. Because the peak value of the pulse is reduced when the insulation resistance is reduced, the monitoring device can detect an abnormality. The monitoring device switches between actuators by using switches that connect or disconnect the actuators to determine a deteriorated part of the insulation resistance.
Patent Literature 1: Japanese Laid-open Patent Publication No. 2012-202723
Patent Literature 2: Japanese Laid-open Patent Publication No. 2008-167617
Patent Literature 3: Japanese Laid-open Patent Publication No. 2013-236486
However, the aforementioned technology does not have sufficient efficiency because the abnormal part is specified after the ignition of the vehicle is stopped.
For example, the ignition of the vehicle may be started immediately after the ignition is stopped depending on situations. In this case, it is impossible to specify a deteriorated part of the insulation resistance. Even when an abnormality in an insulation state of an electric power source is detected during running of the vehicle, it is impossible to specify the deteriorated part of the insulation resistance until the vehicle is stopped. This leads to a mismatch between a situation of the abnormality detection and a situation of details determination. Thus, it is impossible to specify a cause of the deterioration, and the recurrence probability thereof becomes high.